watermarking.py 文件源码

def extractMseq(cover, stego, secret_length, m, tau=1):
    u"""Extract secret informations by spread spectrum using m-sequence.
    @param  cover         : cover data (2 dimensional np.ndarray)
    @param  stego         : stego data (2 dimension np.ndarray)
    @param  secret_length : length of secret information
    @param  m             : M-Sequence
    @param  tau           : embed shift interval
    @return secret        : extracted secret information
    """

    cover = _image2vrctor(cover)
    stego = _image2vrctor(stego)

    m_length = len(m)

    data = stego - cover
    data = data[:m_length:tau]

    secret_data = correlate(m, data, cycle=CYCLE)
    center = ((m_length-1)*2+1)//2
    secret_data = secret_data[center:center+secret_length]
    secret_data = list(map(_checkData, secret_data))

    return secret_data